Cautions For Refrigerant Piping Work; Thickness Of Pipes; Dimensions Of Flare Cutting And Flare Nut; Flare Cutting Dimensions - Mitsubishi Electric PUHZ-RP250YHA2 Service Manual

(2) Cautions for refrigerant piping work

New refrigerant R410A is adopted for replacement inverter series. Although the refrigerant piping work for R410A is same
as for R22, exclusive tools are necessary so as not to mix with different kind of refrigerant. Furthermore as the working
pressure of R410A is 1.6 time higher than that of R22, their sizes of flared sections and flare nuts are different.

Thickness of pipes

Because the working pressure of R410A is higher compared to R22, be sure to use refrigerant piping with thickness
shown below. (Never use pipes of 0.7mm or below.)
Diagram below: Piping diameter and thickness
Nominal Outside
dimensions (inch) diameter (mm)
1/4 6.35
3/8 9.52
1/2 12.70
5/8 15.88
3/4 19.05
7/8 22.20
1 25.40
1-1/8 28.58

Dimensions of flare cutting and flare nut

The component molecules in HFC refrigerant are smaller compared to conventional refrigerants. In addition to that,
R410A is a refrigerant, which has higher risk of leakage because of its working pressure higher than that of other refriger-
ants. Therefore, to enhance airtightness and intensity, flare cutting dimension of copper pipe for R410A have been speci-
fied separately from the dimensions for other refrigerants as shown below. The dimension B of flare nut for R410A also
have partly been changed to increase intensity as shown below. Set copper pipe correctly referring to copper pipe flaring
dimensions for R410A below. For 1/2 and 5/8 inch, the dimension B changes.
Use torque wrench corresponding to each dimension.
Dimension A

Flare cutting dimensions

Nominal Outside
dimensions(inch) diameter
1/4 6.35
3/8 9.52
1/2 12.70
5/8 15.88
3/4 19.05
Tools for R410A (The following table shows whether conventional tools can be used or not.)
Tools and materials
Gauge manifold
Charge hose
Gas leak detector
Refrigerant recovery equipment
Refrigerant cylinder
Applied oil
Safety charger
Charge valve
Vacuum pump
Flare tool
Bender
Pipe cutter
Welder and nitrogen gas cylinder
Refrigerant charging scale
Vacuum gauge or thermis-
tor vacuum gauge and
vacuum valve
Charging cylinder
: Prepare a new tool. (Use the new tool as the tool exclusive for R410A.)
: Tools for other refrigerants can be used under certain conditions.
: Tools for other refrigerants can be used.
Thickness (mm)
R410A R22
0.8 0.8
0.8 0.8
0.8 0.8
1.0 1.0
— 1.0
— 1.0
— 1.0
— 1.0
(mm)
Dimension A ( +0 )
-0.4
R410A R22
9.1 9.0
13.2 13.0
16.6 16.2
19.7 19.4
24.0
23.3
Use R410A tools
Air purge, refrigerant charge and
Tool exclusive for R410A
operation check Tool exclusive for R410A
Tool for HFC refrigerant
Gas leak check
Refrigerant recovery
Tool exclusive for R410A
Refrigerant charge
Tool exclusive for R410A
Apply to flared section
Ester oil, ether oil and
alkylbenzene oil (minimum amount)
Tool exclusive for R410A
Prevent compressor malfunction
when charging refrigerant by
spraying liquid refrigerant
Tool exclusive for R410A
Prevent gas from blowing out
when detaching charge hose
Vacuum drying and air Tools for other refrigerants can
be used if equipped with adop-
purge
ter for reverse flow check
Flaring work of piping Tools for other refrigerants
can be used by adjusting
flaring dimension
Bend the pipes Tools for other refrigerants can be used
Tools for other refrigerants can be used
Cut the pipes
Tools for other refrigerants can be used
Weld the pipes
Tools for other refrigerants can be used
Refrigerant charge
Tools for other refrigerants
Check the degree of vacuum. (Vacuum
valve prevents back flow of oil and refri-
can be used
gerant to thermistor vacuum gauge)
Refrigerant charge Tool exclusive for R410A
Flare nut dimensions
Nominal Outside
dimensions(inch) diameter
1/4 6.35
3/8 9.52
1/2 12.70
5/8 15.88
3/4 19.05
Can R22 tools be used?
(Usable if equipped
with adopter for rever-
se flow)
(Usable by adjusting
flaring dimension)
6
Dimension B
(mm)
Dimension B
R410A R22
17.0 17.0
22.0 22.0
26.0 24.0
29.0 27.0
36.0 36.0
Can R407C tools be used?
Ester oil, ether oil:
Alkylbenzene oil: minimum amount
(Usable if equipped
with adopter for rever-
se flow)
(Usable by adjusting
flaring dimension)